We developed an environmentally friendly mechanochemical protocol to induce an effective Fischer indolisation to synthesize indoles and indolines taking advantage of oxalic acid and dimethylurea.

In just a few years, chemists have significantly changed their approach to the synthesis of organic molecules in the laboratory and industry. Researchers are encouraged to approach “greener” reagents, solvents, and methodologies, to go hand in hand with the world’s environmental matter, such as water, soil, and air pollution. The employment of plant and animal derivates that are commonly regarded as “waste material” has paved the way for the development of new green strategies. In this review, the most important innovations in this field have been highlighted, paying due attention to those materials that have played a crucial role in organic reactions: wool, silk, and feather. Moreover, we decided to focus on the other most important supports and catalysts in green syntheses, such as proteins and their derivates. Different materials have shown prominent activity in the adsorption of metals and organic dyes, which has constituted a relevant scope in the last two decades. We intend to furnish a complete screening of the application given to these materials and contribute to their potential future utilization.

This study presents the first mechanochemical borrowing hydrogenation (BH) strategy, offering a direct and efficient route to N ‐alkylated amines and heterocycles. This solvent‐free approach overcomes many challenges associated with conventional solution‐based syntheses, such as toxic reagents, inert atmospheres, high temperatures, lengthy reaction times, excessive catalyst loadings, and the use of solvents. By applying this method under mechanochemical conditions and employing a readily available ruthenium‐based catalyst, we achieved high conversions of a diverse set of primary amines and alcohols into N ‐alkylated amines. Furthermore, kinetic isotope effect ( KIE ) studies and Hammett analyses provided key insights into the underlying reaction mechanism. Ultimately, this protocol expands synthetic possibilities by facilitating the preparation of heterocycles.

An N-alkylation procedure has been developed under very mild conditions using a known commercially available Ru-based catalyst.